Leaf-miner: Oviposition in the midrib. From there a corridor the larva enters
the lamina which suddenly and strongly widens. The larva finally
pupates in a globular cocoon inside the mine. Because the mine is
formed when the leaf already is fully developed mined leaves have
a normal shape (Bladmineerders van Europa).

The mine is rather flat and not inflated, unlike some other Orchestes species (British
leafminers).

Larva: The larvae of beetles have a head capsule and chewing mouthparts with opposable mandibles and lack abdominal legs (see examples).

Pupa: The pupae of beetles have visible head appendages, wings and legs which lie in sheaths (see examples).

Comments:
According to Hering (1957a) this blotch part is situated against
the leaf margin, and in the distal part of the leaf; this would
separate this mine from that of Tachyerges
stigma. However, Scherf (1964a) writes that at least in
Alnus, the two mines cannot be told apart (Bladmineerders van Europa).